This invention relates to combustion control directed to maintaining fuel efficiency and minimal emissions of air pollutants, especially nitrogen oxides (NOx). More particularly, the invention provides a combustion control system to maintain a selected fuel-air ratio that is improved in that density changes of a reactant, usually air, caused by temperature variations, are compensated for.
A popular combustion control system is based on the use of an electrically operated valve in the fuel supply line which is responsive to variations in the fuel-air pressure ratio. Such a valve is offered by Siemens as the SKP70 pressure regulating electro-hydraulic actuator combined with a Siemens VG series gas valve. This type of fuel-air control is further described in relation to the accompanying drawing which includes the improvement of this invention. This type of control system will hereafter be referred to as the “fuel-air pressure ratio” system for brevity.
A principal object of this invention is to provide an improved combustion control system that in response to temperature changes of the reactants, usually air alone, automatically varies the flow of fuel through a flow regulator to maintain a substantially constant target fuel-air ratio.
Another object is to minimize the use of mechanical linkages in the control system.
These and other features and advantages of the invention will be apparent from the description which follows.